Actuating device for pipe-chamber feeders of hydraulic transport equipments

ABSTRACT

An actuating device for pipe-chamber feeders of hydraulic transport equipments comprising valves or other closing appliances having a closing element that is movable reciprocally between an open and a closed position, the improvement being characterized in said closing element being associated with at least one speed control means, especially a speed reducing means acting at least at the end phase of the closing stroke of said closing element. 
     The speed reducing effect of at least one of said speed control means may be adjustable.

FIELD OF INVENTION

The present invention relates to an improved actuating device forpipe-chamber feeders of hydraulic transporting and hoisting equipmentsadapted to convey solid materials such as coal or slag in the form ofslurry. Such actuating devices generally contain valves and otherclosing appliances and the invention mainly relates to thespeed-controlled actuation of closing elements of these appliances.

BACKGROUND OF THE INVENTION

The function of a pipe-chamber feeder consists of the periodicalalternate filling of the chambers with slurry at low pressure, andemptying them at high pressure. While performing this function, theclosing appliances, especially valves or sliding valves must be openedand closed by a suitable actuating device in a certain sequence and atshort time periods, most advantageously in a manner as it is describedin the Hungarian Patent Specification No. 160 526. However, the closingelements of the valves have to be moved slowly because a quick closingwould cause disadvantageous pressure and velocity fluctuations, evenheavy water impacts that are called water hammer in the art concerned.

Consequently, in prior art devices the change-over or switch-over stepsi.e. the closing and opening of the valves are relatively slow and theyresult in a disadvantageous decrease of the performance of transportequipments having only two pipe chambers. In such equipments everychange-over consists at least of two opening and closing steps, andduring the change-over operations filling or emptying of the pipechambers is not possible.

If three or more pipe-chambers are used there is no such decrease of theoutput. However, investment and operating costs of equipments havingthree or more pipe-chambers are much too high. In addition to this, adiminishing of the time necessary for the switch-over steps is stilldesirable even if the number of pipe-chambers is more than two.

The fact that the change-over steps in the known prior art hydraulictransport equipments are extremely time-consuming is speciallydisadvantageous with large-size equipments because the speed ofactuation of the closing elements of big closing appliances is veryslow, and also the pressure-changes in the large pipe-chambers take muchtime.

SUMMARY OF THE INVENTION

Main object of the invention is to greatly diminish the decrease ofoutput caused by the slow actuation of the valves in known hydraulictransport equipments, especially in those, having two pipe-chamberfeeders, and to attain that even if largest closing elements having aclosing stroke as long as 300 to 600 mm are used, practically no loss incapacity or performance should occur by the change-over operations.Simultaneously, of course, water impacts should also be avoided.

These and other objects are attained by the present invention thatresults in that the closing element of the closing appliances especiallyclosing elements of the main valves are quickly moved, say with a speedthree or four times higher than up to now. Simultaneously with this, theclosing appliances contain one or more means for significantly reducingthe speed of said closing elements at the end phase of their closingstroke i.e. just before arriving at their closed position. It may beimportant that the speed reducing effect should be adjustable and if onespeed reducing throttling device is used only, this is preferred to beadjustable manually. If two or more simultaneously functioning throttledevices are employed, it is important that at least in one of them thethrottling effect should be adjustable.

The slowing down of the closing element can be continuous or stepped.

COMPARISON OF THE INVENTION WITH THE PRIOR ART

There are well known hydraulic stroke-end brakes called cataracts inwhich the speed of a quickly moving piston or other part is slowed downat the end of its stroke by a fluid caused to stream through a narrowopening. However, such hydraulic stroke-end brakes have never beenemployed in valves of hydraulic transport equipments. Thus the basicidea of the invention consists of using such cataracts for increasingthe output of such equipments.

It has been found that by using the invention, a hydraulic transportequipment having two pipe-chamber feeders will have a capacity which wasattained up to now by very expensive three-chamber equipments only.

A further novel feature of the invention is that the throttling effectto be employed at the end of the closing stroke of the closing elementsshould be adjustable so as to be able to alter the slowing effect. Infact when designing the equipment in most cases it is not possible topredict the most advantageous throttling effect and thus the speed atthe end of the closing stroke should be determined experimentally duringthe trial run of every equipment.

A further surprising effect of the invention lies in the following:

The sludge or slurry is filled in the pipe-chamber by means of a pumpworking with low pressure. During this necessary change-over periodsthis filling is interrupted. Consequently, in the known prior artequipments, if the sludge is continuously pumped into the sludgecontainer, the solid particles contained tend to sedimentation duringthe period of change-over, and this may cause serious breakdowns. Thequick change-over operation made possible by the invention is suitableto avoid such breakdowns.

SHORT DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the typical closing characteristics of a slide valve thatis commonly used for filling a pipe-chamber feeder. The figureillustrates that the initial flow resistance caused by closing is smalland changes at the beginning of the closing stroke very little only, butit quickly increases towards the end of the closing stroke. Thestrongest throttling effect is employed at about the last 10% of theclosing movement.

FIG. 2 diagramatically depicts an embodiment of the device according tothe invention shown by way of example only, in which there is a meansfor adjusting the speed of the closing element provided, and there areincluded two further throttle valves for choking the flow of the brakingfluid in two phases at the end-phase of the stroke.

FIG. 3 is a diagramatic sectional view of an oil-hydraulic cylinderadapted to drive the closing element of a closing appliance in a deviceaccording to the invention. In this embodiment the thrusting effectcannot be adjusted, so it is advantageous to use this type of speedreducing means in devices according to the present invention with atleast one further throttling means, preferably throttle valve suitableto adjust the chocking effect manually.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

According to FIG. 2 a pump 2 supplies oil through a reversing valve 3into the upper working chamber of a hydraulic cylinder 4 of theactuating device. The hydraulic cylinder 4 drives a closing element 5Aof a closing appliance by means of a hydraulic piston and a piston rod9. Since there is only a preliminary regulator 6B arranged in thepressure pipe of pump 2, only a very low throttling effect is producedand thus, the full oil pressure drives the piston of the hydrauliccylinder 4 with little resistance, so that the closing element is movedquickly. The preliminary regulator 6B is suitable to adjust the speed ofthe several closing elements if present in the device relatively to eachother.

Oil pressed out from cylinder 4 streams through a preliminary regulator6A which serves for exactly adjusting the quick movement speed of thepiston. It is clear that the choking effect set by the preliminaryregulators 6A and 6B is effective along the whole stroke of the piston.Oil leaving preliminary regulator 6A flows through further change-overthrottle valves 8A and 8B which, in the position shown in the drawing,let through the oil practically without throttling. The oil leaving thechange-over throttle valves 8A and 8B returns to the fluid tank 1 afterpassing again the reversing valve 3.

When the closing element 5A arrives near its closing position, a buffer7 secured to the piston rod 9 reaches a control lever of the change-overthrottle valve 8A and brings this valve against positive spring effectin its throttling position. Consequently the stream of oil coming fromcylinder 4 is throttled by this valve 8A so that the speed of theclosing element 5A is reduced. When said buffer 7 continues its movementit reaches the other change-over throttle valve 8B and it is alsobrought into its throttling position. As a result of this, the speed ofmovement of the closing element 5A becomes still slower. Since theresulting throttling effect is very closely adapted to the valvecharacteristics shown in FIG. 1 of the drawing, no water impact and nodisadvantageous pressure fluctuation will occur upon closing.

Valves 8A and 8B can be regulated or adjusted in order to find aresulting choking effect that is most advantageous for the closingoperation.

If the closing appliance is to be opened, the closing element 5A startsits movement with a slow speed because the oil streaming now in theopposite direction must pass through valves 8A and 8B that are in theirthrottling position. However, when the buffer 7 leaves the valves 8B and8A, they are brought by means of springs in a few seconds sequence intheir non-throttling positions so that the opening movement of theclosing means is speeded up to its full speed.

From the above description it is clear that the device is suitable foradjusting the speed of the closing element in the vicinity of itsclosing position to a certain maximum value of velocity at which waterimpacts and similar harmful effects are surely avoided. Along theremaining part of the stroke, however, the speed can be set of a valueequal to a multiple of said speed. Consequently the change-overoperation of the pipe-chamber feeder takes a very short time periodonly.

Instead of the above described mechanical device also an electronicembodiment may be employed for instance in a way that the buffer 7 onthe piston rod 9 controls an electric or electronic switch which in turncauses a change-over of a valve or of valves. It has already beenproposed to move the closing elements by means of electromagnets insteadof a hydraulic piston, and according to the invention, also in suchembodiments it is possible to control the speed of movement of theclosing element in a manner that a strong electromagnet first quicklydrives the closing element at the beginning of its closing stroke and atthe end-phase of its closing stroke near the valve seat the speed ofthis element is reduced.

DESCRIPTION OF A SECOND PREFERRED EMBODIMENT

According to FIG. 3 a plunger body 13 and a piston rod 12 of a hydraulicpiston 10 are arranged in a cylinder 4A with sliding fit. Two extensions14 and 15 situated between said plunger body 13 and said piston rod 12have a smaller diameter than the inner diameters of stepped portions 16and 17 of the hydraulic cylinder 4A respectively. The stepped portions16 and 17 are made in that end part of the hydraulic cylinder 4A whichis turned towards the closing element to be actuated which is not shownin FIG. 3 but can be clearly seen in FIG. 2.

The position of the piston 10 shown in FIG. 3 in dotted linescorresponds to its end position in which the closing element not shownin FIG. 3 /and driven by the hydraulic piston/ is in its fully openedposition. If now the hydraulic fluid is fed into the hydraulic cylinder4A through inlet channel 11A, the piston starts its closing movementwith a very high speed, because the oil on the other side of thehydraulic piston 10 may leave through a chanel 11B practicallyunthrottled. The speed of the hydraulic piston 10 is shown by V_(o) inthe diagram of FIG. 3.

When the hydraulic piston 10 attains the position shown in full in FIG.3, throttling of the flow of oil begins, because in course of thefurther movement of the hydraulic piston 10 the oil is compelled to passthrough the narrow cylindric interspace between the extention 14 and thefirst stepped portion 16 of the hydraulic cylinder 4A. Streaming throughthis cylindrical interspace means a certain throttling of the flow andthus, the speed of the piston is reduced to a value V₁ as shown in theabove mentioned diagram in FIG. 3 of the drawing.

When the hydraulic piston 10 continues its stroke of travel, also thesecond extension 15 comes into the area of the second stepped portion 17and as a result, a double throttling effect occurs. The speed of thehydraulic piston 10 further diminishes to the value V₂, so that theclosing movement of the closing element driven by the hydraulic piston10 is accomplished by a slow speed as generally required in hydraulictransport equipments. Of course, for performing the above ask, channel11B opens into the very end portion of the hydraulic cylinder 4A i.e. itjoins the narrowest end section of said cylinder 4A.

If the closing element connected to the piston rod 12 is to be openedthe high pressure oil enters the hydraulic cylinder 4A through thechanel 11B and initially a double throttling effect prevails. After ashort time the oil streams under single throttling resistance only, andwhen the piston 13 arrives to the position shown in full lines in FIG.3, it continues its movement under full pressure and with maximal speedV_(o).

The invention is not limited to the two stepped throttling embodiment asdescribed above by way of example only. In some cases a singlethrottling can be sufficient or, on the contrary even more than twosteps are necessary.

Since the device as shown in FIG. 3 of the drawing cannot be adjustedmanually to the best throttling effect, it is advantageous to combinethis embodiment with at least one further adjustable throttling device.

We claim:
 1. An improved actuating device for pipe-chamber feeders ofhydraulic transport equipment, said actuating device comprising valvesor other closing appliances having a closing element that is movablereciprocally between an open and a closed position by a hydraulic pistonthat is moved in a hydraulic cylinder, said closing element beingassociated with a plurality of throttling means adapted to have a speedreducing effect that increasingly reduces the speed of said closingelement as it more nearly approaches its closed position, the speedreducing effect of at least one of said throttling means beingadjustable as to its initial and ultimate throttling effect andcomprising a throttle valve, that is inserted into at least onepipe-line feeding or leading away hydraulic fluid into or out from saidhydraulic cylinder and said throttling means being activated in sequenceby an activating member associated with a piston rod connecting saidhydraulic piston and said closing member.
 2. An improved actuatingdevice for pipe chamber feeders of hydraulic transport equipment, saidactuating device comprising valves or other closing appliances having aclosing element that is movable reciprocally between an open and aclosed position by a hydraulic piston that is moved in a hydrauliccylinder, said closing element being associated with at least oneadjustable and variably throttling means adapted to have a speedreducing effect that increasingly reduces the speed of said closingelement as it more nearly approaches its closed position, the speedreducing effect of said at least one adjustable and variably throttlingmeans being adjustable as to its initial and ultimate throttling effectand comprising a throttle valve that is inserted into at least onepipe-line feeding or leading away hydraulic fluid into or out from saidhydraulic cylinder, and an adjustable constant throttling means beingalso associated with the hydraulic pipelines.
 3. An improved actuatingdevice as claimed in claim 2, wherein said constant throttling meansaffects flow in the hydraulic pipelines only in one direction.
 4. Animproved actuating device as claimed in claim 2, wherein said at leastone throttling means being adjustable manually.
 5. An improved actuatingdevice as claimed in claim 2 wherein the throttling effect of said atleast one throttling means is effective substantially over the wholestroke of said closing element.
 6. An improved actuating device asclaimed in claim 1, wherein the activating member has a contouredactivating surface, the contour of which controls the rate of changefrom the initial to the ultimate throttling effect of said adjustablevariably throttling means activated by said activating member.